1. Field of the Invention
This invention relates to a wiper control device for actuating a wiper device mounted, for example on a motor vehicle and especially to a device for controlling the wiper device which is so designed as to change the rotational direction of the wiper motor between cases of high-speed operation and low-speed operation of the motor and decrease substantial length of a motor arm of the wiper linkage at the time of the high speed operation as compared with that of the motor arm at the time of the low speed operation through an arm-length adjusting device including an eccentric mechanism attached on the motor arm of the linkage in order to solve a difference in the wiping ranges at the time of high speed operation and low speed operation caused by a difference of inertial force of the wiper blade.
2. Description of the Prior Art
As an apparatus for wiping rain drops adhering to the windshield of the motor vehicle and ensuring the wide visual range of a driver, wiper apparatuses having various structure and function have been used. Recently, a wiper apparatus which is designed so as to be possible to select working speed of the wiper blade between continuous operation of two-level at high and low speeds and intermittent operation at a low speed according to the amount of rain-fall is used generally.
In the wiper apparatus of this kind, kinetic energy of the wiper blade at he time of high speed operation (high-speed mode) becomes larger than that of the wiper blade at the time of low speed operation (low-speed mode), therefore a phenomenon is observed in that the wiping range of the wiper blade at the time of high-speed operation becomes wider as compared with the wiping range at the time of low-speed operation of the wiper blade according to the difference in the inertial force of the wiper blade. Accordingly, there is defectiveness in that the windshield partially remains unwiped and the visual field becomes narrow at the time of low speed operation in a case where the wiping range of the windshield is set on basis of the oscillation range of the wiper blade at the time of high speed operation and the wiper blade runs out of the windshield glass at the time of high speed operation in a case where the wiping range of the windshield is set on basis of the oscillation range of the wiper blade at the time of high speed operation.
Applicant proposed previously a wiper linkage which was so designed as to solve the difference in the actual wiping range enlarged owing to addition of the inertial force of the wiper blade by setting the rotational direction of the wiper motor at the time of high speed operation conversely against that of the wiper motor at the time of low speed operation, making the substantial length of the motor arm of the wiper linkage at the time of high speed operation shorter than that of the motor arm at the time of low speed operation through an arm length adjusting mechanism attached to the motor arm and used with an eccentric bush to be turned as much as 180xc2x0 at the time of switching over the rotational direction of the motor arm and reducing the structural wiping range of the wiper blade at the time of high speed operation as compared with that of the wiper blade at the time of low speed operation in Japanese Patent Application No.10-158026/98 in order to remove the difference in the wiping range caused by the difference in the operation speed of the wiper blade in the conventional wiper apparatus of the two-speed type.
In the newly proposed wiper linkage as mentioned above, however, it is different foundamentally from the conventional wiper linkage in the point that the rotational directions of the wiper motor at the high speed operation and the low speed operation are different from each other, so that there are various problems differing from the conventional linkage in switching control of the wiper mode (high-speed mode and low-speed mode), auto-stop control at the time of stopping the wiper apparatus and so on. For example, it becomes necessary to supply an electric current by changing the brush terminals of the wiper motor at the same time of changing the direction of the electric current in a case the wiper mode is changed over from the low-speed mode into the high-speed mode or from the high-speed mode into the low-speed mode, and the wiper blade goes back at the middle of the wiping range on the windshield glass, whereby not only a strange impression is given to the passengers, but also an unwiped area remains on the windshield glass until the wiper blade comes back from the turning position in a case where the rotational direction of the wiper motor is changed regardless of the position of the wiper blade. So that there is a problem in that it is necessary to perform special control differing from the conventional wiper linkage, and development of the wiper control device has become on subject, which is suitable for the wiper linkage so designed as to remove the difference in the wiping range caused by the difference in the operation speed of the wiper blade by changing the rotational direction of the wiper motor between the low speed operation and the high speed operation.
This invention is made in view of the aforementioned problem in the control of the wiper linkage of which wiper motor is different in the rotational direction between low speed operation and high speed operation, and it is an object to provide a wiper control device which is possible to smoothly switch over the rotational direction of the wiper motor together with the rotational speed and execute the control without causing the strange impression and the unwiped area at the time of changing the operation speed and stopping the wiper blade.
In order to accomplish to the aforementioned object, the wiper control device according to this invention is provided with a wiper switch, a wiper motor, a position switch, a controller and a motor driving circuit, and the controller is so designed as to change the rotational direction of the wiper motor at the time when the wiper blade arrives in the lower turning position or the upper turning position after the low-speed command signal or the high-speed command signal generated from the wiper switch is switched over into the high-speed command signal or the low-speed command signal, respectively. Namely, in the case where the wiper switch is switched over from the low-speed mode to the high-speed mode, or from the high-speed mode to the low speed mode, the rotation of the wiper motor is switched over from the low-speed forward rotation to the high-speed reverse rotation, or from the high-speed reverse rotation to the low-speed forward direction when the wiper blade arrives at either the lower turning position or the upper turning position, that is when the wiper linkage is in the dead point, therefore the unnatural phenomenon is solved in that the wiper blade goes back at the middle of the windshield glass according as the rotational direction of the wiper motor is changed.
In the wiper control device according to a preferred embodiment of this invention, the position switch is provided with a high-potential plate connected with the power source, a low-potential plate grounded, a clutch member rotatable by being pushed against a push member rotating together with the output shaft of the wiper motor only in a direction energized by the push member, and a movable contact attached to the clutch member so as to slidingly come in contact with the high and low-potential plates. Namely, the movable contact is not secured to the output shaft of the wiper motor and the wiper blade and so structured as to stay in the present position while the output shaft of the wiper motor makes nearly one revolution in a case where the wiper blade moves backward, or the rotational direction of the wiper motor is changed. Accordingly, the chattering of the wiper blade caused by obstacles such snows, and the signal change is obtained suitably for reversing control of the wiper motor from the movable contact by setting the openings between the high and low-potential plates in correspondence to the upper and lower turning positions of the wiper blade, respectively.
In the wiper control device according to another preferred embodiment of this invention, the motor driving circuit forms a current supplying circuit through the movable contact and the low-potential plate of the position switch when the controller does not generate neither the low-speed driving signal nor the high-speed driving signal, and the wiper motor is supplied with an electric current in the low-speed forward-rotational direction through the current supplying circuit while the movable contact is in contact with the low-potential plate of the position switch. Therefore, the wiper blade stops automatically in the predetermined position in response to disappearance of the low-speed driving signal and the high-speed driving signal after off-operation of the wiper switch.
In the wiper control device according to the other preferred embodiment of this invention, the position switch is set so as to produce a change in the position signal at the time when the wiper blade arrives at a position predetermined in just before the lower turning position, therefore improper behavior is solved in that the wiper blade stops after passing the lower turning position (home position) by inertia, or moves backward on the windshield glass by the inverting rotation of the wiper motor after passing through the lower turning position. In the wiper control device according to the other preferred embodiment of which position switch is set so as to produce a change in the position signal at the time the wiper blade arrives in a position predetermined in just before the upper turning position in a case where the wiper motor is rotated forwardly in the low speed, the changeover of wiper mode from the low-speed mode to the high-speed mode is carried out speedily by switching over the rotation of the wiper motor into the high-speed reverse rotation from the low-speed forward rotation at the time when the wiper blade is in the upper turning position.
Further in the wiper control device according to the other embodiment of this invention, the device is further provided with a circuit for supplying the position signal on low level to the controller when the movable contact arrives in an opening formed between the high and low-potential plates of the position switch in a case where the controller outputs the high-speed driving signal, and supplying the position signal on high level to the controller when the movable contact arrives in the opening formed between the high and low-potential plates in a case where the controller does not output the high-speed driving signal. Therefore, the controller recognizes the opening to be the high-potential plate at the time of low speed operation and recognizes the opening to be the low-potential plate at the time of high speed operation, and the change is caused in the position signal at the time when the wiper blade arrives at the position predetermined in just before the turning position regardless of the operation speed or the rotational direction of the wiper motor, so that the wiper blade turns accurately at the turning position and stops accurately at the lower turning position without passing the turning position by inertia.
In the wiper control device according to the other preferred embodiment of this invention, the controller is so designed as to interrupt the output of the high-speed driving signal at the time when the wiper blade arrives at a position predetermined in just before the lower turning position after disappearance of the high-speed command signal from the wiper switch. Accordingly, time required for the wiper blade to be stopped automatically in the home position (lower turning position) after off-operation of the wiper switch is reduced since the wiper mode remains in the high-speed mode until the wiper motor begins to rotate in the forward direction at the low speed through the current supplying circuit after arrival of the wiper blade in the lower turning position.
In the wiper control device according to the other desirable embodiment of this invention, the controller switches over the low-speed driving signal into the high-speed driving signal at the time when the wiper blade arrives at a predetermined position just before the lower turning position or the upper turning position after the low-speed command signal from the wiper switch is changed into the high-speed command signal, and the controller interrupts the output of the high-speed driving signal at the time when the wiper blade arrives at the predetermined position just before the lower turning position after the high-speed command signal from the wiper switch is changed into the low-speed command signal and generates the low-speed driving signal at the time when a period of time predetermined sufficiently longer than time required for the movable contact to pass the opening formed between the high and low-potential plates of the position switch elapses after the arrival of the wiper blade at the predetermined position just before the lower turning position. Therefore, in the case where the low-speed mode is switched over to the high-speed mode, the wiper mode is speedily switched because the driving signal is changed not only when the wiper blade arrives in the position just before the lower turning position, but also when it arrives in the position just before the upper turning position. Furthermore, in the case where the high-speed mode is switched over to the low-speed mode, the high-speed driving signal is interrupted first when the wiper blade arrives in the position just before the lower turning position, and then the low-speed driving signal is supplied after the movable contact passes completely through the opening existing between the high and low-potential plates of the position switch, therefore a large electric current does not flow in the relays even when the rotational direction of the wiper motor is changed, whereby load of the relays is lightened and reliability of the relays is improved.
In the wiper control device according to the other preferred embodiment of this invention, which is provide with a backup circuit, the backup circuit is so designed as to supply an electric current to the wiper motor in the low-speed forward-rotational direction or the high-speed reverse-rotational direction through the motor driving circuit in accordance with operation of the wiper switch at the time when a watchdog signal becomes extinct by failure of the controller. Therefore it is possible to relieve the serious situation in that the wiper blade falls completely to a standstill even if the controller breaks down unexpectedly owing to some reason.
Furthermore, in the wiper control device according to the other embodiment of this invention, the wiper motor is provided with a first terminal connected to a common brush, a second terminal connected to a low brush and a third terminal connected to a high brush, and the motor driving circuit is provided with four relays, first and second transistors of which emitters are grounded and bases are connected to a high-speed driving signal output port and a low-speed driving signal output port of the controller, respectively; ends of respective relay coils of the four relays are connected with the power source, the other ends of the respective relay coils of the first, second and third relays among the four relays are connected to the collector of the first transistor, another end of the relay coil of the fourth relay of the four relays is connected to the collector of the second transistor; a moving contact and a normal-closed contact of the first relay are connected to the power source and the second terminal of the wiper motor, respectively; a moving contact of the second relay is grounded and a normal-closed contact of the second relay is connected to the third terminal of the wiper motor; a moving contact, a normal-opened contact and a normal-closed contact of the third relay are connected to the first terminal of the wiper motor, the power source and a moving contact of the fourth relay, respectively; and a normal-closed contact of the fourth relay is connected to the movable contact of the position switch and a normal-opened contact of the fourth relay is grounded. Therefore, the second transistor is turned to the on-state according to the output of a high-level signal (low-speed driving signal) from the low-speed driving signal output port of the controller, and an electric current is supplied to the wiper motor from the second terminal (low brush) to the first terminal (common brush) through the fourth relay switched on, thereby rotating the wiper motor in the forward direction in the low speed. On the other side, the first transistor is turned to the on-state according to the output of a high-level signal (high-speed driving signal) from the high-speed driving signal output port of the controller, and an electric current is supplied to the wiper motor from the third terminal (high brush) to the first terminal (common brush) through the first, second and third relays switched on, thereby rotating the wiper motor in the reverse direction in the high speed. Furthermore, in the case where the controller does not supply neither the low-speed driving signal nor the high-speed driving signal, all the relays become the off-state, however the wiper motor continues to rotate in the forward direction at the low speed by forming the current supplying circuit during the movable contact of the position switch is on the low-potential plate grounded, and the wiper motor is stopped by forming an armature short circuit when the movable contact comes in contact with the high-potential plate after separating from the low-potential plate of the position switch.
In the wiper control device according to the other embodiment of this invention, which is provided with the circuit having two resistors connected to the power source in series and a diode connected between a node of the two resistors and the collector of the first transistor, the other end of the two resistors is connected in the middle of a connection wire between the movable contact of the position switch and a position signal monitoring port of the controller and the diode permits an electric current to pass through toward the first transistor. The position signal on low-level is supplied to the position signal monitoring port of the controller even when the movable contact of the position switch is on the opening between the high and low-potential plates in a case where the high-level signal (high-speed driving signal) is generated form the high-speed driving signal output port of the controller because the mode of the two resistors is grounded through the diode and the first transistor in on-state. The other side, the position signal on high-level regulated through the two resistors is supplied to the position signal monitoring port of the controller even when the movable contact is on the opening between the high and low-potential plates of the position switch in a case where the high-speed driving signal is not generated from the controller because the first transistor is in the off-state.
In the wiper control device according to the further preferable embodiment of this invention, which is provided with the backup circuit including further two transistors, two diodes and two capacitors, the second diode is connected between the third and fourth transistors, the third diode is connected between the fourth transistor and a terminal of the wiper switch to be grounded by operating the wiper switch into the high-speed mode and permits an electric current to pass through toward the wiper switch; emitter of the third transistor is grounded, collector and base of the third transistor are connected to the power source and a watchdog signal output port of the controller through the first capacitor, respectively; collector and base of the fourth transistor are connected to the other end of the relay coil of the fourth relay in the motor driving circuit and cathode of the second diode, respectively; and anode of the second diode is connected to collector of the third transistor and grounded through the second capasitor. In the case where the watchdog signal from the watchdog signal output port of the controller becomes extinct, the third transistor becomes to the off-state and the fourth transistor becomes to the on-state, so that the relay coil of the fourth relay is excited through the third diode and the wiper switch, thereby switching on the fourth relay and rotating the wiper motor in the forward direction at the low speed by operating the wiper switch into the high-speed mode.